Studies on the structure of macromolecules in cancer cells are essential for defining the biochemical lesion(s) distinguishing cancer cells from normal cells. This research proposal concerns 3 related topics: (1) A methodological investigation of postlabeling procedures for the sequence analysis of non-radioactive RNA; (2) Sequence analysis of specific, 5-methylcytidine-rich tRNAs; (3) Studies on the effects of antineoplastic drugs (5-azacytidine, 5-fluorocytidine) on tRNA and DNA as well as tRNA methyltransferases and DNA methyltransferases. COMMENTS: Methods to be developed for the structural analysis of minute amounts of non-radioactive RNA will entail 3H-labeling and 32P-labeling, enzymatic and chemical digestions, chromatographic and electrophoretic separations. We wish to determine the sequences of tRNAs that are rich in 5-methylcytidine because 5-azacytidine and 5-fluorocytidine were found in our laboratory to inhibit specifically the formation of this compound in nucleic acids. Preparation of nucleic acids deficient in a single constituent may enable one to define the biological role(s) of this constituent. In vivo studies are planned to investigate the effects of 5-azacytidine and 5-fluorocytidine on tRNA and DNA. In vitro studies will be aimed at elucidating the mechanisms of inhibition of RNA and DNA methylation by the nucleoside analogs.